Photodestruction of BDE-99 in micellar solutions of nonionic surfactants of Brij 35 and Brij 58.

Currently, soil contamination by polybrominated diphenyl ethers (PBDEs) at e-waste recycling sites in China is of significant environmental concern and requires the identification of appropriate remediation technologies. In this paper, photodestruction of a model PBDE congener (BDE-99) in selected UV/surfactant systems was investigated, using a RPR-200 Rayonet photochemical reactor equipped with two low-pressure mercury lamps. BDE-99 photodegradation in the micellar solutions of nonionic surfactants of Brij 35 and Brij 58 all followed pseudo first-order kinetics and the photodegradation quantum yields were 1.8-2.4 times as high as that in water alone. The photodegradation was comparably enhanced by Brij 35 and Brij 58, and the quenching effect of dissolved oxygen (DO) was eliminated in their presence. Mono- to tetra-BDEs were identified as one group of BDE-99 photoproducts, indicating that one of BDE-99 photodegradation pathways was through a sequential loss of Br. The pattern of PBDE photoproducts showed the photodebromination of BDE-99 readily occurred on the more heavily substituted phenyl ring. Mono- to tetra-polybrominated dibenzofurans (PBDFs) were identified as another group of photoproducts, indicating BDE-99 can also photodegrade through a dibenzofuran-type ring closure process via an intramolecular elimination of HBr. In addition, the formation of these more toxic photoproducts (PBDFs) was not related to the presence of DO. Finally, the later disappearance of mono-BDEs and mono-BDFs suggested the UV exposure time would be an important technical parameter if the technology of UV photodestruction of PBDEs in surfactant micellar solutions is applied to PBDE-contaminated soil remediation.